A positioning drive for a motor vehicle door closing device, particularly for a motor vehicle central locking mechanism, can comprise an electric motor, a transmission, a gear/spindle unit and a positioning element mounted in a housing. The positioning element is extendible and retractable by alternating action of the gear/spindle unit.
The positioning element is for example connected to the operating lever of a motor vehicle door closing device and positions it in the locked position or the theft preventing position.
In the known positioning drive the positioning element is extendible with the help of an electric motor and retractable also by reversing the poles of the motor. To this aspect the positioning drive is a servo controlling the lock mechanism or a slave system responsive to a master control.
According to the mechanism of the motor vehicle door closing device this can be a problem. It is a drawback, for example, in the case when a motor vehicle door closing device locked by the central locking mechanism should be opened manually from the vehicle interior. Then the positioning element must be returned by manual force using the appropriate device on the motor vehicle door closing device in synchronization with the transmission and the electric motor. In other applications of this positioning drive the conditions are similar when a kimenatic reversal in regard to extension and retraction is required.